title: Critical period of memory enhancement during taste avoidance conditioning in Lymnaea stagnalis.
abstract: The present study investigated the optimal training procedure leading to long-lasting taste avoidance behavior in Lymnaea. A training procedure comprising 5 repeated pairings of a conditional stimulus (CS, sucrose), with an unconditional stimulus (US, a tactile stimulation to the animal's head), over a 4-day period resulted in an enhanced memory formation than 10 CS-US repeated pairings over a 2-day period or 20 CS-US repeated pairings on a single day. Backward conditioning (US-CS) pairings did not result in conditioning. Thus, this taste avoidance conditioning was CS-US pairing specific. Food avoidance behavior was not observed following training, however, if snails were immediately subjected to a cold-block (4°C for 10 min). It was critical that the cold-block be applied within 10 min to block long-term memory (LTM) formation. Further, exposure to the cold-block 180 min after training also blocked both STM and LTM formation. The effects of the cold-block on subsequent learning and memory formation were also examined. We found no long lasting effects of the cold-block on subsequent memory formation. If protein kinase C was activated before the conditioning paradigm, snails could still acquire STM despite exposure to the cold-block.
authors.affiliation: School of High-Technology for Human Welfare, Tokai University, Numazu, Shizuoka, Japan.
authors.forename: Tomoyo
authors.initials: T
authors.lastname: Takahashi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Takigami
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sunada
authors.forename: Ken
authors.initials: K
authors.lastname: Lukowiak
authors.forename: Manabu
authors.initials: M
authors.lastname: Sakakibara
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000502:physiology*; D003213:Conditioning, Psychological / Q000502:physiology*; D008195:Lymnaea; D008568:Memory / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism; D013649:Taste
chemical_list: D011493:Protein Kinase C